Weed dynamics and their management in sugarcane under different preceding crops and tillage systems

A field experiment was conducted during 1998-2002 to study the effect of preceding crops and tillage systems on population dynamics of weeds in sugarcane crop and its yield and quality in relation to weed management. The sugarcane crop faced intense competition with sedges (abundance index > 4) at tillering stage (60 days after planting) irrespective of preceding crops, viz wheat (Triticum aestivum L. emend. Fiori & Paol.) or Indian mustard [Brassica juncea (L.) Czemj. & Cosson], and tillage systems, viz conventional or minimum. At the onset of grand growth (120 days after planting), the weed flora was influenced with the extent of rainfall, as grasses took over the field (abundance index > 4) from sedges in the second crop cycle that received good rainfall. Indian mustard as preceding crop caused significantly higher weed density in sugarcane (60.1 and 67.5/m(2) in 1999-2000 and 2000-01) compared with that after wheat (47.4 and 58.1/m(2)) at 60 days after planting. Effect of tillage systems on weed density and dry matter production in sugarcane crop was, however, inconsistent over the crop stages and seasons. Significantly higher cane yield owing to management of weeds through hoeing (64.1 and 84.7 tonnes/ha) as well as herbicides (58 and 70.4 tonnes/ha) was obtained over weedy check (49.9 and 33.9 tonnes/ha) that caused 22.1 and 59.9% loss in cane yield during the first and second crop cycles respectively.